The invention relates to mounting devices, especially those useful in automotive engine or powertrain mounts that are used to impede undesirable vibrations from reaching the passenger compartment. Elastomeric springs in series separated by "closed" geometric shapes, e.g., cylinders, squares, rectangles, etc., have been tried in similar applications but have demonstrated a lack of the required durability. This is due to the fact that all elastomers exhibit resilient curing stress when molded between two "closed" shapes, e.g., concentric cylinders. The primary method of removing these unwanted stresses would be to swage the outer and inner metals sufficiently to reduce the elastomer dimension and thus the resilient curing stress between the two closed shapes.
Briefly stated, the invention is an automotive mount which essentially comprises an open or non-rigid outer cylindrical metal shell which is radially spaced from a rigid inner hollow metal core which has a unique generally tear-shaped cross-section. At least two resilient elastomeric springs are provided between the inner core and outer shell of the mount.
An open or non-rigid parti-cylindrical metal spring is positioned between the elastomeric springs which are in series. In practice this places three springs in series; one is metal, the other two elastomeric. ##EQU1##
The non-rigid intermediate also provides a friendly interface between the two elastomeric spring members in that it tends to equalize forces between these members since it is relatively free to move radially to correct this unbalance.
The metal spring or intermediate member has strategically located metal ears or tabs which project from the spring to form a combination which possesses its own tuneable spring rate as well as supplying an additional intermediate mass to the mount. The tabs can also supply increased resistance to axial displacement. Changes in the size and shape of the tabs will result in changes in the response of the mounting. The metal spring is also provided with slots or voids which provide a tuning mechanism along with the physical dimensions, i.e., thickness, width, etc. Changes made individually or collectively in these elements result in a changed response in the mount. In other words, they may be used to tune the mount for a specific environment in multi directions.
In addition, the closure of the outer open member during assembly into a mounting bracket produces a swaging effect on the elastomeric elements without performing two swaging operations.